Much like Paul Rudd and Ant-Man, it's been common knowledge that Vin Diesel was set to play walking, talking space tree Groot in Marvel's upcoming Guardians Of The Galaxy, but there was no official word... until now.

Posting the image above onto his Facebook page, director James Gunn had several very nice things to say about the Fast & Furious star. "Yep, it is completely official. AND he’s amazing. I never knew someone could say 'I AM GROOT' so many different ways and with such feeling (and that sounds like I’m kidding but I’m not!)."

Diesel has plenty of experience in the voice acting world, as anyone who's made it through The Iron Giant without crying will testify (ha! As if such a person exists). Hopefully his time walking about in mechanised stilts will have helped to develop his arboreal gait and get in the mindset of a tree.

Guardians finds Chris Pratt as Peter Quill (AKA Star Lord), a wise-cracking human pilot who gets tangled up with a group of renegades and mercenaries who eventually bond together as a mismatched superhero team. Other cast members already hard at work include Zoe Saldana, Lee Pace, Benicio Del Toro, John C. Reilly, Glenn Close, Dave Bautista, Karen Gillan, Djimon Hounsou, Ophelia Lovibond and, as a talking raccoon with a taste for explosive weaponry, Bradley Cooper.

He kind of was. Not officialy, but if it was not true, Marvel would have already denied the rumors like they do with other high profile actors that certainly are not gonna take a role.
Same with Paul Rudd being cast as Ant-Man. After JGL landed the Sandman job, it was pretty obvious, that Paul would get the role. More